1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member having a photosensitive layer in which a disazo pigment having a specific structure is present, as well as an electrophotographic apparatus and a facsimile which employ such an electrophotographic photosensitive member.
2. Description of the Related Art
Typical examples of the organic photoconductive substances for use in an electrophotographic photosensitive member include: photoconductive polymers, such as poly-N-vinyl carbazole; low-molecular organic photoconductive substances, such as 2, 5-bis (p-diethylaminophenyl)-1, 3 and 4-oxadiazole; and various combinations of such organic photoconductive substances and dyes or pigments.
Electrophotographic photosensitive members which employ such organic photoconductive substances have advantages in that productivity is high, that they are inexpensive, and that color sensitivity thereof can be freely controlled by selecting the pigment or dye used. Therefore, research has heretofore been conducted on electrophotographic photosensitive members. The function separation type photosensitive member has been developed in which a charge generating layer containing an organic photoconductive dye or pigment and a charge transporting layer containing any of the above described photoconductive polymers or low-molecular organic photoconductive substances are disposed as a laminate. Accordingly, the sensitivity and durability of the conventional organic photoelectric photosensitive members have thus been improved greatly.
Among organic conductive substances, azo pigments in general exhibit excellent photoconductivity. Compounds exhibiting the desired characteristics can be produced relatively easily by combining azo components with coupler components. Therefore, various types of compounds have heretofore been proposed. Such compounds are disclosed in, for example, Japanese Patent Laid-Open Nos. 22834/1979, 131539/1985, 215556/1986, 241763/1986, 24261/1988 and 158561/1988.
In recent years, there has been a demand for a higher image quality. To meet this demand, organic photoconductive substances which can provide an electrophotographic photosensitive member exhibiting higher sensitivity and more stable potential characteristics have been desired.